The present invention is a synthetic crystalline zeolite (hereinafter referred to as ECR-26) which is a transition metal substituted form of the mineral gmelinite.
Gmelinite is a well-known natural zeolite having a structure in which the main feature is a large 12-ring channel, and in this regard it is analogous to zeolites Linde L, mordenite, and cancrinite. All previously reported compositions contain only Si and Al in framework sites, and have a propensity to form intergrown materials comprising atomic level intergrowths of gmelinite and chabazite. All known natural varieties are thought to be of this type, resulting in a blocked 12-ring channel and poor sorption properties resulting from a variety of possible intergrowths (G. T. Kokotailo and S. L. Lawton, Nature, 203, p. 621, (1964)). The only known gmelinite materials having open 12-ring channels are made with a DABCO polymer filling the channels (L. D. Rollman, NATO ASI Ser. E-60, "Zeolites: Science and Technology", R. Ribeiro et al, p. 109, (1984)). ECR-26 is an open channel chromiumalumino-silicate gmelinite which requires no organic template for its synthesis. The Cr.sup.3+ presumably inhibits the formation of phases which normally intergrow with gmelinite, facilitating the growth of the perfect open structure.
Materials of this general structure are important catalysts and sorbents, particularly in hydrocracking and hydroisomerization (mordenite) and aromatization and reforming (zeolite L). Similar important catalyst applications are anticipated for ECR-26, and because the transition metal may be manipulated into non-framework sites, important Fischer-Tropsch applications are possible.